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Class _ 

Book IKJ. 




UNITED STATES DEPARTMENT OF AGRICULTURE 

BULLETIN No. 632 

Contribution from the Bureau of Plant Industry 
WM. A. TAYLOR, Chief 





Washington, D. C. 



PROFESSIONAL PAPER 



November 30, 1917 



THE UTILIZATION OF WASTE TOMATO SEEDS 
AND SKINS. 

By Fbank Rabak, Chemical Biologist, Drug-Plant and Poisonous-Plant Investi- 
gations, Bureau of Plant Industry. 



CONTENTS. 



Page, 

troduction 1 

mmercial products from tomato refuse 1 

■cumulation and disposal of tomato waste. . 3 

Percentages of seeds and skins 3 

Dryine the waste material and separat- 
ing the seeds 5 

ctraction of tomato-seed oil 5 

Physical and chemical properties of the 

crude and the refined oil: 7 



Page- 
Extraction of tomato-seed oil— Continued. 

Chemical examination of the oil 7 

Available quantity of the oil 9 

Uses and value of the oil 10 

Tomato-seed meal 11 

Utilization for stock feeding 11 

Available quantity of the meal 12 

Summary 12 

Literature cited 14 



INTRODUCTION. 

The manufacture of tomato products in the United States con- 
stitutes an industry of large and growing proportions and impor- 
tance. Tomatoes serve as the basis for two general classes of prod- 
ucts, in one of which the fresh whole tomatoes are used and in the 
other the pulp alone, as in the manufacture of catsups and soups. 
For this latter class large quantities of tomatoes are required, from 
which the seeds and skins at present are discarded as useless. 

The increased interest in the production of foodstuffs throughout 
the country will doubtless result in an extension of all canning and 
packing operations, including tomato products. In the following 
pages attention is directed to the possible utilization of the waste 
tomato material, not only from the standpoint of food conservation, 
but as a profitable adjunct to the tomato-canning industry. 

COMMERCIAL PRODUCTS FROM TOMATO REFUSE. 

By proper treatment, tomato refuse may be made to produce 

two important products, namely, fixed oil and meal, both of which 

180l>5°— 17 



CvK 



2 BULLETIN 632, U. S. DEPARTMENT OF AGRICULTURE. 

possess considerable value. The seeds of the tomato contain a fatty 
oil of excellent quality, and the seed cake is valuable as a stock food. 

Considerable work has already been done in foreign countries, 
especially in Italy, on the utilization of tomato waste. Battaglia 
(4) 1 in 1901 investigated tomato-seed oil and reported on its prop- 
erties. Later, Kochs (9), in an investigation of certain residue-, 
mentioned tomato-seed oil and discussed its properties, stating that 
17.3 per cent of oil having an agreeable taste and smell could be ob- 
tained from the seeds. 

In the manufacture of tomato products, Italy perhaps leads all 
countries. The industry there has assumed such proportions that 
the problem of the proper disposal of the residues has become an 
important consideration. Perciabosco and Semeraro (12) in 1910 
investigated tomato residues with a view to extracting the fatty oil, 
determining also the industrial value of the oil and the fertilizer 
and feeding values of the residues after extraction. The oil ex 
tracted by carbon bisulphid was found to have properties similar to 
those of the oil previously reported by Battaglia. The fat-free 
residues were found to be useful for fertilizing purpose-. 

Harcourt (6) in 1907 called attention to the tomato refuse ac- 
cumulating in increasing quantities at the canning factories in 
Canada. It was reported that a large portion of the refuse was 
flushed into near-by rivers, but in some cases it was allowed to 
accumulate near the factories, thus becoming a nuisance. Some of 
the refuse was spread over the land as a fertilizer. The mammal 
value was tested and found to compare favorably with barnyard 
manure in the three important elements, potash, phosphoric acid, 
and nitrogen. 

Accomazzo (1) in 1910 stated that in the province of Parma, Italy. 
850,000 quintals (83,660 tons) of tomatoes were used annually. This 
quantity would yield from 11,000 to 12,000 tons of skins and seeds, 
containing about 80 per cent moisture. After removing the greater 
portion of the moisture the residue would amount to about 3,000 to 
4,000 tons, of which about two-thirds are seeds. It is stated that 
these seeds when extracted by pressure yield 18 per cent of oil and 
by solvents 20 per cent. It would therefore be possible to recover 
from 500 to 600 tons of oil from the waste seeds. Tomato-seed oil 
is stated to have a heat value about equal to that of olive oil. When 
treated with driers it acquires good drying properties and is al-«> 
useful in soap making. The press cake is said to have excellent 
nutritive value. 

Fachini (5) also recommends the extraction of oil from the seeds, 
but instead of drying the residue, as proposed by Accomazzo, he 

lr Tne serial numbers In parentheses refer to "Literature cited," pp. 14-15. 

p; of d; 

dec 10 'mr 






UTILIZATION OF WASTE TOMATO SEEDS AXD SKINS. 3 

suggests a method of separating the seeds from the skins by agitat- 
ing the material with water and allowing it to settle, whereupon the 
seeds fall to the bottom. The greater part of the water can then be 
removed from the wet seeds by centrifugal machines, after which 
the seeds are dried easily and the oil can be removed by extraction 
or pressure. 

According to Consul Keena (5). Florence. Italy, the utilization 
of tomato waste and the extraction of the oil from the seeds was 
first attempted by a firm in Parma in 1910. The success of the 
undertaking led to the establishment of two other factories the fol- 
lowing year. About 5.000 metric tons (1 metric ton=2.204 pounds) 
of wet tomato waste, corresponding to 1.500 metric tons of dry waste. 
were worked out for the extraction of the oil and manufacture of 
the meal. These operations yielded 150 tons of oil. 800 tons of oil 
cake, and 500 tons of tomato skins. 

Tomato-seed oil has been utilized in the manufacture of soap, and 
the conversion of the crude oil into an edible oil is also receiving 
attention. The press cake is used in the manufacture of stock feed, 
while the skins are suggested as a fertilizer. 

The seeds are sold at Parma for 14 cents per 100 pounds, while at 
Xaples the wet residue is sold at 4 to 8 cents per 100 pounds. This 
residue, which ferments readily, must be collected and dried daily. 
When dry it sells at 81.75 to 82.20 per 100 pounds. 

More recently attention has been called by Shriver ( 11 1 to the vast 
quantities of tomato seeds and skins accumulating as waste products 
from the rapidly growing canned-tomato industry in Italy. The 
problem of the proper disposition of this waste has been receiving at- 
tention since 1908. at which time a manufacturing plant was estab- 
lished in Milan, with branch drying plants at Parma. Ceriale. Cervia. 
Piacenza. and Pilastro. 

The oil is sold in the crude state for 87 per 100 pounds, and the 
refined oil for 88.75 per 100 pounds. The press cake is mixed with the 
skins and other ingredients and sold as stock feed. 

The yield of oil from the seeds is stated by Shriver to be about 20 
per cent by pressure and 22 per cent by solvents. In 1913. from 100 
to 150 metric tons of oil and 1.000 metric tons of stock feed were 
manufactured in Milan from the press cake and skins. 

Bailey and Burnett (3"). working with American tomato seeds, ex- 
tracted the oil by pressure and found that it could be refined and 
bleached easily and was apparently a satisfactory food oil. 

ACCUMULATION AND DISPOSAL OF TOMATO WASTE. 

PERCENTAGES OF SEEDS AND SKINS. 

For the preparation of tomato pulp, the fresh tomatoes, after being 
carefully sorted to remove the. culls, are thoroughly washed by a 



4 BULLETIN 632, U. S. DEPARTMENT OF AGRICULTURE. 

stream of water under pressure, then passed into receptacles where 
they are cooked with steam, and afterward are transferred to a 
cyclone machine, which removes the pulp. The seeds and skins pasfi 
out and are discarded. By the cold process the washed tomatoes 
pass directly to the cyclone machine. 

The total quantity of tomato waste which accumulates annually 
in the United States depends not only upon the pack of any particu- 
lar season but also upon the percentage of seeds contained in the 
fresh tomatoes. The seed content varies with the variety of tomato. 
Estimated from the figures given by Accomazzo (1), Italian-grown 
tomatoes contain 14.7 per cent of Avet waste, of which about 80 per 
cent is water. After removing the greater portion of the water, 
the waste amounts to 4.8 per cent. Of this waste, which probably 
still contains some moisture. 73 per cent is seeds. The dry waste a> 
it occurs in Italy is stated to contain about G6 per cent by weight of 
seeds (15). These percentages are considerably higher than the 
results obtained from American-grown tomatoes. 

Two experiments in different localities were made with American- 
grown tomatoes which had been used for pulping purposes, to de- 
termine the percentage of seeds and skins. The quantity of fresh 
tomatoes used in the two experiments was 2,320 pounds and 5,344 
pounds, respectively. The results were as follows: Wet waste, 5.43 
and 5.44 per cent; dry waste, 1.11 and 0.95 per cent. The dry waste 
in these experiments contained 46.3 and 42.8 per cent seeds and 58.7 
and 57.2 per cent skins, respectively. 

According to Street (16, p. 128-129), fresh tomatoes contain L.35 
per cent dry waste, consisting of 49.3 per cent seeds and 50.7 per 
cent skins. Using these figures as a basis for calculation, American- 
grown tomatoes contain on the average about 1.13 per cent dry waste, 
of which 46.1 per cent is seeds and 53.9 per cent skins. Fresh toma- 
toes therefore contain the equivalent of 0.52 per cent dry seeds and 
0.61 per cent dry skins. 

In order to learn the approximate annual output of tomato refuse 
in the United States, the writer personally visited 21 of the Lai 
tomato-pulping firms. These manufacturing concerns operate Largely 
in Indiana, Iowa. Michigan, and Ohio in the Middle West, and New 
Jersey. Pennsylvania. New York, Delaware, and Maryland in the 
East. Detailed figures regarding the output of refuse were not 
available in each State. The extent of the industry, however, may 
be realized when it is learned that in Indiana alone L20,000 tons of 
tomatoes are pulped annually. Applying the percentages previously 
mentioned, the amount of dry waste in this one State would be about 
1.356 tons, or 624 tons of seeds and 732 tons of skins. 

Not all the firms engaged in pulping tomatoes could be reached; 
therefore accurate information in regard to the total quantity used 



UTILIZATION OF WASTE TOMATO SEEDS AND SKIXS. 

annually could not be obtained. But from the figures given by the 
firms visited, supplemented by correspondence with other firms, it is 
estimated that 275,000 tons are pulped annually. Adding to this the 
tonnage of culls, from which also the seeds and skins could be sepa- 
rated, a conservative estimate would be about 300,000 tons. 

This tonnage, of course, would vary from year to year. However, 
owing to the increasing demand for tomato products, the tonnage 
will tend to increase each year. 

The quantity of wet waste resulting annually would be about 
16,000 tons, which would yield approximately 3,000 tons of dry 
waste. This dry waste would yield about 1,500 tons of dry seeds 
and 1,800 tons of dry skins. 

DRYING THE WASTE MATERIAL AND SEPARATING THE SEEDS. 

An important problem in connection with the utilization of tomato 
waste is the drying of the mass and separating the seeds from the 
skins. According to Shriver (14. p. 21-22), this problem is handled 
in Italy in the following manner: 

The wet seeds and skins are passed through a press to remove as much of 
the moisture as possible. They are then passed through a desiccator, or drier, 
in which the material is kept in constant motion by means of horizontal con- 
veyers, finally emerging from the machine in a dry condition. Heat is applied 
to the drier by means of steam pipes or by forced air. 

It is stated that about 10 tons of residue can be dried in 24 hours. 
The final operation consists in passing the dried material through a 
machine supplied with a series of sieves and fans, which results in 
the complete separation of the seeds from the skins. 

A number of types of desiccators, or driers, are manufactured in 
the United States which would be admirably suited for drying the 
wet waste. It has been suggested that a sugar-beet drier would 
handle the material efficiently. Xo great difficult}- should be ex- 
perienced in constructing a separator consisting of sieves and fans 
for the separation of the seeds from the skins. 

EXTRACTION OF TOMATO-SEED OIL. 

Two methods of extraction are applicable for obtaining fatty oil 
from seeds. The pressure method is perhaps the simplest and most 
expeditious, being well adapted to seeds containing a fairly high per- 
centage of oil. The most careful manipulation of this proces-. how- 
ever, leaves a residual portion of the oil in the press cake. The ex- 
peller type of press is perhaps the best adapted for seeds having 
is comparatively low percentage of oil. Even with this type of ma- 
chine a small percentage of oil remains in the press cake. This, how- 
ever, is not a total loss, since the value of the cake is enham-ed by 
the presence of some fat. A distinct advantage of the pressure 



BULLETIN 632, U. S. DEPARTMENT OF AliKlCl'I.TURE. 

method is in the better quality of the product obtained. Pressed oils 
usually contain less impurities and consequently are more readily 
and effectively refined. 

When the maximum percentage of oil is desired from certain ma- 
terials the volatile-solvent method of extraction serves best. Tin- 
principal solvents which may be employed are benzine, petroleum 
ether, gasoline, and carbon tetrachlorid. A disadvantage of this 
method is in the inflammability of many of the solvents, necessi- 
tating careful handling and operation. This trouble is largely over- 
come by the use of carbon tetrachlorid, which is noninflammable and 
possesses a higher boiling point than any of the other solvent- and 
hence is capable of effecting more complete recovery. Oils obtained 
by the solvent extraction method are usually less pure than expressed 
oils, containing much coloring matter and other impurities extracted 
by the particular solvent employed. No great difficulty is experi- 
enced, however, in refining the oils thus obtained. Pressed oils also 
require refining. 

Apparatus of the continuous-extraction type is usually employed. 
This kind of apparatus minimizes the quantity of solvent used and 
prevents loss of the solvent during the operation. Practically all the 
solvent may be recovered from the oil and residue and thus be avail- 
able for further use. A practical example of the use of a volatile 
solvent for the extraction of fatty oil is the use of benzine in the ex- 
traction of soy-bean oil (11). The disadvantages of the solvent 
method as compared with the advantages of the pressure method 
are largely offset by the lower cost of the apparatus, the smaller ex- 
pense of operation, and the higher yield of oil obtainable. 

Continuous extractors and hydraulic presses are obtainable from 
American manufacturers of chemical and pharmaceutical machinery. 

Either of the two methods mentioned may be used effectively in 
the extraction of oil from tomato seeds. The solvent extraction 
method was used for obtaining the samples in the experiment- de- 
scribed in this bulletin. The apparatus employed was the contin- 
uous-extraction type, the solvents used being ether and carbon tetra- 
chlorid. The yield of oil from the ground seeds with either solvent 
was practically the same, averaging ±1 per cent. The crude oil was 
pale greenish yellow in color with a fatty, slightly rancid odor and 
fatty, slightly bitter taste. 

In refining the crude oil the objectionable odor was removed by 
passing steam through the oil until little or no odor was perceptible. 
The deodorized oil was then heated on a steam bath for about one 
hour with fullers earth (kaolin) and finally filtered while hot 
through filter paper. This procedure effected decolorization of the 
oil to a marked degree. The refined oil possessed a very pale yel- 
lowish color with bland fatty and agreeable nutlike taste and smell 



UTILIZATION Or WASTE TOMATO SEEDS AND SKINS. 7 

PHYSICAL AND CHEMICAL PROPERTIES OF THE CRUDE AND THE REFINED OILS. 

Some of the more common physical and chemical constants of the 
crude and the refined oils -were determined, as shown in Table I. For 
purposes of comparison the properties of some of the tomato-seed 
oils of foreign origin are also included in the table. 

Table I. — Physical and chemical constants' 1 of tomato-seed oil from domestic 
and foreign tomatoes. 





Domestic oil. 


Foreign 


investigators. 




Physical 

and chemical 

constants. 


Crude. 


*•*»*• Lsi). 


Battaglia 
(4). 


Kochs (9). 


Percia- 
z ;;:: i~i 

(12). 










Brownish red. 

Agreeable, to- 
matolike. 
do 

0.920c 






low. 

Fatty, nutlike. 
slightly rancid. 










like.' 


0.922 c. . . 
1 4730... 




Specific gravity. 


bitter. Eke; no bitter 
aftertaste. 
09216* ftmsio 1 0020c 


0.9244.C 


1.4694* 

Turbid at 0' C: 


1 4:7U<* . 






tion. 


Turbid at 2° C; 




Thick liquid 
at -9= C. 

1S3.6.'."!!!"" 
117.8 




Acid value 

Saponification 
value. 


yellow gelati- 
nous mass at 

-rc 

8.8 

190.4 


solid, very pale i 
vellow mass at 1 
-10" C. 

Mai™"™"!" "Msie™ 

114.2 KD 


26.3 

190.4.... 

106.9.... 


1.823. 
1S9.4. 


108 













a Determined according to standard methods (17). & At 24* C. « At 15° C. * At 25° C. 

From Table I may be noted the general effect of the refining 
process upon the physical and chemical properties of the oil. The 
color, odor, and taste of the refined oil show much improvement over 
the same properties of the crude oil. The specific gravity and index 
of refraction show changes due to the removal of impurities by the 
refining process. The congealing point of the refined oil has likewise 
changed. The acid value is materially lower than that of the crude 
oil, owing to the removal of the free fatty acids. The saponification 
and iodin values show similar differences due to the removal of im- 
purities. 

Among the oils of foreign origin the properties reported by Bat- 
taglia correspond more nearly to those of the crude oil of domestic 
origin, while the remainder compare favorably in most cases with the 
refined domestic oil. 



CHEMICAL EXAMINATION OF THE OIL. 



In addition to the chemical constants a further examination of the 
refined oil was made to determine its approximate composition. The 
determinations were made according to standard methods 1 17. p. 
138-139). No soluble acids were found, but 96.2 per cent of insoluble 



8 



BULLETIN 632, U. S. DEPARTMENT OF AGRICULTURE. 



acids were present. These insoluble acids were separated into the 
solid and liquid acids by means of the lead-ether method (17, p. 4.")). 
The mixed acids were found to consist of solid acids 17.54 per cent 
and liquid acids 75.84 per cent. 

The physical and chemical properties of the insoluble acids and the 
solid and liquid acids, were determined with the results shown in 
Table II. 



Table II. — Physical and chemical properties of insoluble, solid, and liquid OOidt 
of tomato-seed oil. 



PhySiCa irop n erti^ hemiCal ' Insoluble acids. 


Solid acids. 


Liquid acids. 


Color Pale golden yellow; 

partly solid. 


Snowy white, flaky 


Pale golden yellow 




Fatty, tallowlike 






coming sligtulv bitter. 
0.9013. 
1.4664. 






■2o° C. 






204 19-' '-i 






130. 







The solid acids, comprising 17.54 per cent of the oil. probably 
consist largely of palmitic and stearic acids with neutralization 
values of 219.1 and 197.5, respectively. The neutralization value 
204 would indicate a mixture of these two acids. Although the melt- 
ing point of crude solid acids is considerably lower than either 
palmitic or stearic acids, which melt when pure at 62° ('. and 09° C, 
respectively, it is very probable that this is due to the presence of 
impurities. 

Calculating from the neutralization value 204, the mean molec- 
ular weight of the solid acids was found to be 275. This indicates 
the presence of palmitic and stearic acids, since the molecular weight 
of these acids are 256 and 284, respectively. 

In order to ascertain the approximate proportions of these two 
acids in the mixed solid acids, a calculation was made according 
to the method suggested by Lewkowitsch (10, v. 1, p. 515), using as 
a basis 275, the mean molecular weight of these solid acid-. By 
this method, the percentage of palmitic acid was found to be 67.8 
and of stearic acid 32.2. 

Since 17.54 per cent of the original oil consists of solid acids, the 
oil therefore contains palmitic acid 11.88 per cent and stearic acid 
5.G4 per cent. Because the palmitic and stearic acids exist in the oil 
as palmitin and stearin, it is necessary to reduce the above figures 
to terms of these glycerids. The glycerid palmitin contains 95.29 
per cent of palmitic acid, and the glycerid stearin contains !>5.73 
per cent of stearic acid. By calculation, therefore, it is found that 



UTILIZATION OT WASTE TOMATO SEEDS AND SKINS. 9 

tomato-seed oil contains 12.47 per cent of palmitin and 5.89 per 
cent of stearin. 

The liquid acids, constituting 75.84 per cent of the oil. possess 
properties which indicate the presence of oleic acid and possibly 
some linoleic acid. 

The specific gravity of the liquid acids, 0.9013 at 25 z C. 
would indicate a mixture of oleic and linoleic acids, since the specific 
gravity of pure oleic acid is 0.893 at 25° C. and linoleic acid 0.9206 
at 14° C. The index of refraction corresponds closely with oleic 
acid, which possesses an index of refraction of 1.4603 at 25° C. 

The neutralization value of 192-3 is somewhat lower than that of 
pure oleic acid. 198.9. and pure linoleic acid. 200.4. The iodin value. 
130, possibly also indicates a mixture of oleic and linoleic acids 
with a preponderance of oleic acid. Some commercial oleic acids 
have idoin values as high as 100 to 110. while pure linoleic acid 
possesses an iodin value of 181.42. 

Using the method of Lewkowitsch (10. v. 1. p. 457). for calculating 
the approximate proportions of oleic and linoleic acids present from 
the iodin value as a basis, it was found that the liquid acids consist of 
56.8 per cent of oleic acid and 43.2 per cent of linoleic acid. Reducing 
these percentages of oleic and linoleic acids to terms of the original 
oil. which consists of 75.84 per cent of liquid acids, it is found that 
the oil contains approximately 43.07 per cent of oleic acid and 32.76 
per cent of linoleic acid. These acids are contained in the oil in 
the form of the glycerids olein and linolein, which contain 95.7 and 
95.67 per cent, respectively, of oleic and linoleic acids. By calculation 
it is found, therefore, that the oil consists approximately of 45 per 
cent of olein and 34.2 per cent of linolein. 

A summary of the results of the chemical examination of tomato- 
seed oil indicates the following approximate composition : Olein. 45 
per cent: linolein. 34.2 per cent: palmitin. 12.47 per cent: stearin, 
5.89 per cent — the remaining portion consisting of free acids and 
unsaponifiable matter. 

AVAILABLE QUANTITY OF THE OIL. 

Estimating the annual output of dry tomato waste from the various 
pulping plants in the United States at 3.390 tons, there would result 
from this waste 1.560 tons of dry seeds. The quantity of oil capable 
of being extracted from these seeds is readily ascertained. Since by 
extracting with volatile solvents 22 per cent of the oil can be ob- 
tained, the total available quantity would be about 343 ton- annually. 
This quantity would, however, increase each year with the increased 
output of tomato products. 



10 BULLETIN rJ32, U. S. DEPARTMENT OF AGRICULTURE. 

USES AND VALUE OF THE OIL. 

Classifying fatty oils as drying, semidrying, and nondrying, to- 
mato-seed oil possibly falls into the semidrying class, bordering, 
however, very nearly on the nondrying class. In order that the na- 
ture of tomato-seed oil may be better understood, a comparison is 
given in Table III of some of the more important properties of a 
number of oils of commerce belonging in the same class with tomato- 
seed oil (10, v. 2). 

Table III. — Physical and chemical properties of tomato-seed oil and several 
important oils of commerce. 



Oils. 


Specific gravity 
at 15° C 


Congealing 
point (°C). 


Saponification 
value. 


Iodin value. 


Index of 
refraction 






Turbid at —2; 
pale yellow 
solid " mass 
at -10. 


188.6 

191 to 196. 5 
190. 6 to 192. 9 
187. 6 to 194. 6 
188 to 193. 4 


114.2 

100. 9 to 116. 9 
121 to 124 
103 to 115 
112 to 130. 8 


b 1. 4715 




0.922 to 0.930... 
0.924 to 0.927... 
0. 9203 to 0. 9260.. 
0.9213 


1.4722 


witsch (10, p. 149-150). 


+15 to + 8.... 
- 4 to- 6.... 
-10 to -20... 




(10, p. 123). 
Sesame, Lewkowitseh 

(10, p. 173). 
Corn, Lewkowitseh (10, 

p. 131-132). 


1.4728 
1 1.4768 







The similarity of tomato-seed oil to the commercial oils given in 
Table III indicates the classification of this oil. The oils mentioned 
in connection with tomato-seed oil are applied commercially in a 
number of ways. As edible oils they are highly prized. On account 
of their drying properties some are employed extensively in the 
manufacture of paints and varnishes, while others find important 
application as soap stock. 

Tomato-seed oil, with properties similar to cottonseed, soy-bean, 
sesame, and corn oils, should be equally useful and applicable to the 
same purposes as these oils of commerce. 

Experiments conducted with tomato-seed oil by Dr. A. D. Holmes, 
of the Office of Home Economics, U. S. Department of Agriculture, 
to determine its digestibility, showed that the oil possesses a coeffi- 
cient of digestibiLity of 97, comparing favorably with olive, almond, 
cottonseed, peanut, coconut, sesame, walnut, and brazil-nut oils. 
Well-refined tomato-seed oil is therefore to be recommended for 
culinary purposes. As a salad oil it should prove very satisfactory. 
The edible quality of the oil suggests also its possible hydrogenation 
and application as a margarine oil. 

An experiment to determine its saponifying properties was con- 
ducted in order to obtain information regarding its possible use 
as soap stock. By cold saponification with caustic soda and subse- 



UTILIZATION OF WASTE TOMATO SEEDS AND SKINS. 



11 



quent salting and pressing, a soap of good texture with excellent 
lathering qualities was produced. If combined with oils rich in 
palmitin or stearin, satisfactory toilet soap doubtless could be pre- 
pared. Owing to the present threatened shortage of oils for the 
manufacture of soaps and glycerine the utilization of tomato-seed 
oil as a soap stock asserts itself. 

Experiments to determine the drying properties of the oil showed 
that 16 days were required to form a soft, sticky film. The nature 
of the film as well as the time of drying could in all probability be 
improved and hastened by the addition of siccatives or driers to the 
oil. It appears, therefore, that the oil possesses a certain value as 
a paint or varnish oil. 

The value of the oil in commerce would necessarily depend upon 
the particular use to which it could be applied and to the demand 
in general for fatty oils. From the results of the investigation, it 
appears that it should prove a valuable addition to the edible or 
condimental oils now in use. Likewise it should find an important 
place among the much-needed soap oils of commerce. 

TOMATO-SEED MEAL. 

UTILIZATION FOR STOCK FEEDING. 

The residue remaining after extracting the oil from the seeds 
constitutes the meal. The utilization of this meal as stock feed is 
suggested. In order to ascertain the approximate composition of 
the meal, a careful analysis was made. The results are shown in 
Table IV. together with analyses of some commercial stock feeds 
as given by Henry and Morrison (7. p. 631r-636). 

Table IT. — Composition of tomato-seed meal as compared with various commer- 
cial stock feeds. 







Constituents ("per cent). 




Feeding stuff. 


Moisture. 


Ash. 


Protein. 


Xitrosen- 

free 
extract. 


Fiber. 


Ether 

extract. 






4.64 
6.6 
4.2 
10.7 
4.3 
7.9 
5.6 


37.0 
39. S 
34.8 
37.5 
16.8 
31.2 


29.10 

27.4 

21.8 

21.7 

35.0 

an.n 


22.11 
10.1 
10.9 
6.3 
24.0 
11.3 






7.8 


*.3 




10.0 


18.3 




9.8 


















9.6 


36.9 36.3 















In moisture and ash content, the tomato-seed meal compares favor- 
ably with the other feed stuffs. In protein content, it ranks with sun- 
flower seedcake, cottonseed meal, sesame-oil cake, rape seedcake, and 
linseed meal, being considerably higher than palm-nut cake and some- 



12 BULLETIN 632, U. S. DEPARTMENT OF AGRICULTURE. 

what lower than cottonseed meal. Since the tomato-seed meal which 
was subjected to analysis was from ether-extracted seeds, the ether 
extract does not enter into consideration. The meal from seed ex- 
pressed by hydraulic pressure would contain from 5 to 7 per cent 
ether extract, which represents the residual fat left in the cake. 
The crude-fiber content is relatively high as compared with the other 
feeds, being lower, however, than that of palm-nut cake. The content 
of nitrogen-free extract, consisting largely of carbohydrates, is higher 
than in such meals as cottonseed, sunflower, and sesame, and lower 
than in palm-nut, rape-seed, and linseed cake. 

From the results of the analysis and the comparison with standard 
stock feeds it would appear that tomato-seed meal possesses proper- 
ties of considerable value for stock feeding. In this connection it 
may be stated that in Italy, where the utilization of tomato residues 
is in practical operation, experiments with the meal or cake have 
demonstrated its value as a feed for stock. Aguet (2) has reported 
a factory in operation at San Giovanni a Teduccio, near Naples, for 
the industrial manufacture of tomato seedcake. Feeding trials con- 
ducted at the Royal Higher School of Agriculture at Portici with 
milch cows showed tomato seedcake to be equal in food value to lin- 
seed cake. Later, Scarpitti (13) conducted extensive investigations 
with the seedcake as a feed for milch cows, stating that it is richer 
than flaxseed cake in protein and fat and is superior to it in its 
influence upon the weight and lacteal secretion of the cows. 

Shriver (14, p. 21-23) describes the manufacture of stock feed 
from the dried tomato waste after the extraction of the oil. A num- 
ber of grades of stock feed under the name " Nutritivo " are manu- 
factured by a firm at Milan, Italy, from the dried skins mixed with 
molasses and the meal from the extracted seeds. This feed for 
cattle is sold at prices ranging, according to quality, from $1.32 
to $1.49 per 100 pounds. The seedcake after the oil is expressed is 
sold at $1.32 per 100 pounds. 

AVAILABLE QUANTITY OF THE MEAL. 

After extracting the oil from the estimated quantity of tomato 
seeds which accumulate annually, there would remain as a by-product 
about 1,200 tons of the meal. In addition to this large quantity 
of meal there would also be available about 1,800 tons of tomato skins. 
In view of the use to which the dried skins are applied in Italy 
by incorporating them with the meal, this would increase the total 
available quantity to about 3,000 tons. 

SUMMARY. 

The foregoing investigation shows that the vast quantities of to- 
mato refuse accumulating each year at tomato-pulping factories can 



UTILIZATION OF WASTE TOMATO SEEDS AND SKINS. 13 

be reduced to two products, namely, fixed oil and meal, each of which 
may be made commercially useful. 

The oil from the seeds should find ready disposal as an edible oil 
or as a soap oil. as shown by the experiments made to determine its 
applicability to these purposes. By proper treatment it can be made 
useful as a drying oil for pamt and varnish purposes. 

The meal has been shown by analysis and comparison with other 
meals to possess valuable qualities as stock feed, and the utility of 
the meal for this purpose should therefore be assured. 

The accumulation of tomato residues occurs principally in two sec- 
tions of the United States, namely, the Xorth-Central States lying 
east of the Mississippi and north of the Ohio Eivers and the Xorth 
Atlantic States. The reduction of this waste material to oil and 
meal could be handled most logically by establishing reducing plants 
at some central point in each of these sections, where the crude ma- 
terial could be collected with the least expense for transportation and 
handling. A cooperative plan of manufacture would perhaps be the 
most feasible and effective method for establishing the industry upon 
a practical basis. 

In view therefore of the threatened shortage of fatty oils and in 
the interest of food conservation, tomato refuse may be considered as 
an available source for the manufacture of oil and oil cake. As the 
demand for tomato products increases, the quantity of this waste 
material will also increase, and it is suggested as an economic measure 
of both agricultural and industrial importance that the utilization 
of this material be considered. 



Gaylord Bros, 

Makers 

Syracuse N. Y. 

PAT. JUL 21, 190* 



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